Battery charge indication methods, battery charge monitoring devices, rechargeable batteries, and articles of manufacture

ABSTRACT

Battery charge indication methods, battery state of charge monitoring devices, rechargeable batteries, and articles of manufacture are described. According to one aspect, a battery charge indication method includes first determining a state of charge of a battery at a first moment in time using a first method, second determining a state of charge of the battery at a second moment in time using a second method different than the first method, and providing information regarding the state of charge of the battery at the first and second moments in time using information of the first and second determinings.

This application is a continuation of application Ser. No. 11/394,726filed Mar. 31, 2006.

TECHNICAL FIELD

This invention relates to battery charge indication methods, batterycharge monitoring devices, rechargeable batteries, and articles ofmanufacture.

BACKGROUND OF THE INVENTION

The sophistication and uses of electrical devices have increaseddramatically. Consumer items having electrical components are ubiquitousin communications, computing, entertainment, transportation, etc.Numerous people rely upon or have grown accustomed to usage ofelectrical devices for business, education, or for other needs.Electronic devices are increasingly portable to accommodate these needsduring travels from home or the workplace. The sophistication andcapabilities of power supplies for such devices have also improved tomeet the requirements of the electronic consumer devices. For example,cost, size, and capacity are some product characteristics which havebeen improved for the portable power supplies. In addition, portablepower supplies are being used in additional applications. For example,there is increased interest upon usage of alternative energy sourcesincluding electrical energy for an expanding number of applications,such as transportation applications.

Exemplary portable power supplies such as batteries store electricalenergy. It may be beneficial to know the state of charge of thebatteries during operation of the electrical devices. However,challenges are presented with respect to determining state of chargeinformation with respect to some battery cell chemistries. In oneexample, it may be difficult to monitor battery cells which have asubstantially flat discharge profile.

At least some aspects of the disclosure provide methods and apparatusfor monitoring charge of batteries.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of the disclosure are described below withreference to the following accompanying drawings.

FIG. 1 is a functional block diagram of an electrical system accordingto one embodiment.

FIG. 2 is a functional block diagram of a battery according to oneembodiment.

FIG. 3 is a functional block diagram of a monitoring device according toone embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

This disclosure of the invention is submitted in furtherance of theconstitutional purposes of the U.S. Patent Laws “to promote the progressof science and useful arts” (Article 1, Section 8).

According to one embodiment, a battery charge indication methodcomprises first determining a state of charge of a battery at a firstmoment in time using a first method, second determining a state ofcharge of the battery at a second moment in time using a second methoddifferent than the first method, and providing information regarding thestate of charge of the battery at the first and second moments in timeusing information of the first and second determinings.

According to another embodiment, a battery charge indication methodcomprises monitoring a battery during discharging of the battery in afirst discharge cycle, using the monitoring, generating informationregarding the discharging of the battery in the first discharge cycle,recharging the battery after the discharging of the battery in the firstdischarge cycle, providing information regarding a state of charge ofthe battery during discharging of the battery in a second dischargecycle after the recharging, and wherein the providing the informationregarding the state of charge comprises providing using the informationregarding the discharging of the battery in the first discharge cycle.

According to yet another embodiment, a battery charge monitoring devicecomprises an interface configured to couple with a battery andprocessing circuitry coupled with the interface and configured toprovide information regarding a state of charge of the battery at aplurality of different moments in time, wherein the processing circuitryis configured to use a first method to determine the informationregarding the state of charge at a first moment in time and to use asecond method different than the first method to provide the informationregarding the state of charge at a second moment in time.

According to still another embodiment, a rechargeable battery comprisesat least one rechargeable cell configured to store electrical energy andto be electrically discharged during a discharged mode of operation andto be electrically charged during a charged mode of operation, and amonitoring device coupled with the at least one rechargeable cell andconfigured to implement a first method to provide information regardingthe state of charge of the rechargeable cell at a first moment in timeand to implement a second method to provide information regarding thestate of charge of the rechargeable cell at a second moment in time,wherein the first and second methods are different.

According to still another embodiment, an article of manufacturecomprises media comprising programming configured to cause processingcircuitry to perform processing comprising first monitoring a firstelectrical parameter of a battery at a first moment in time, firstproviding information regarding a state of charge of the battery at thefirst moment in time using the first monitoring, second monitoring asecond electrical parameter of the battery at a second moment in time,wherein the first and second electrical parameters are different; andsecond providing—Information regarding a state of charge of the batteryat the second moment in time using the second monitoring.

Referring to FIG. 1, an electrical system 10 is depicted according toone embodiment. Electrical system 10 includes a load 12 configured toconsume electrical energy and a battery assembly 13 configured to storeelectrical energy for consumption by load 12. In one embodiment, batteryassembly 13 includes a battery 14 and a monitoring device 16. Battery 14may be rechargeable in one embodiment and charge circuitry 20 may beprovided to charge battery 14 when desired or appropriate.

Battery assembly 13 may include a housing (not shown) configured tohouse battery 14 and monitoring device 16 in one arrangement. Chargecircuitry 20 and/or monitoring device 16 may or may not be includedwithin the housing. In addition, battery 14 and/or monitoring device 16may be external to load 12 in other embodiments.

Monitoring circuitry 16 is configured to perform monitoring operations,such as monitoring a state of charge of battery 14 and/or monitoring theenvironment (e.g., temperature) in which battery 14 is used. Monitoringdevice 16 may monitor battery 14 via an interface 18, such as anelectrical coupling or bus, in one embodiment.

FIG. 2 illustrates an exemplary configuration of battery 14 according toone embodiment. Battery 14 includes negative and positive terminals 22,24 and one or more cells 26 coupled in series intermediate terminals 22,24 in the illustrated configuration. Cells 26 may also be coupled inparallel or in serial/parallel combinations in other possiblearrangements. In one embodiment, cells 26 may be individuallyimplemented as a rechargeable cell which has a substantially flatdischarge profile and which may be recharged between different dischargecycles. Cells 26 may be embodied as Lithium-Ion 3.2 Volt cells embodyingSaphion® technology in a battery having product number 18695-00001available from Valence Technology, Inc. in but one possibleimplementation.

For example, cells 26 may individually comprise an electrode activematerial in one embodiment represented by the general formula A_(a)MPO₄,where A is Li, and 0<a≦1; and M=MI_(n-p)MII_(o), wherein o=p, 0<o≦0.5,MI is iron (Fe), and MII is selected from the group consisting of Be²⁺,Mg²⁺, Ca²⁺, Sr²⁺, Ba²⁺, and mixtures thereof.

In a more specific embodiment, the electrode active material may berepresented by the general formula A_(a)M_(m)(PO₄)₃, where A is Li, and0<a≦5, and M is selected from the group consisting of Ti³⁺, V³⁺, Cr³⁺,Mn³⁺, Fe³⁺, Co³⁺, Ni³⁺, Mo³⁺, Nb³⁺, and mixtures thereof, and 1<m≦3; andwhere A, M, a and m are selected so as to maintain electroneutrality ofthe electrode active material. Additional details regarding exemplarycells 26 are disclosed in U.S. Pat. No. 6,136,472 to Barker et al, U.S.Pat. No. 4,477,541 to Fraioli, International Publication No. W001/54212;International Publication No. W098/12761; International Publication No.W000/01024; International Publication No. W000/31812; InternationalPublication No. W000/57505; International Publication No. W002/44084;International Publication No. W003/085757; International Publication No.W003/085771; International Publication No. W003/088383; U.S. Pat. No.6,528,033 to Barker et al; U.S. Pat. No. 6,387,568 to Barker et al.;U.S. Publication No. 2003/0027049 listing Jeremy Barker et al asinventors; U.S. Publication No. 2002/0192553 listing Jeremy Barker et alas inventors; U.S. Publication No. 2003/0170542 listing Jeremy Barker etal as inventors; U.S. Publication No. 2003/0129492 listing Jeremy Barkeras inventor; U.S. Pat. No. 5,700,298 to Shi et al.; U.S. Pat. No.5,830,602 to Barker et al.; U.S. Pat. No. 5,418,091 to Gozdz et al.;U.S. Pat. No. 5,508,130 to Golovin; U.S. Pat. No. 5,541,020 to Golovinet al.; U.S. Pat. No. 5,620,810 to Golovin et al.; U.S. Pat. No.5,643,695 to Barker et al.; U.S. Pat. No. 5,712,059, to Barker et al.;U.S. Pat. No. 5,851,504 to Barker et al.; U.S. Pat. No. 6,020,087 toGao; U.S. Pat. No. 6,103,419 to Saidi et al.; U.S. Pat. No. 4,668,595 toYoshino et al.; U.S. Pat. No. 4,792,504 to Schwab et al.; U.S. Pat. No.4,830,939 to. Lee et al.; U.S. Pat. No. 4,935,317 to Fauteaux et al.;U.S. Pat. No. 4,990,413, to Lee et al.; U.S. Pat. No. 5,037,712 toShackle et al.; U.S. Pat. No. 5,262,253 to Golovin; U.S. Pat. No.5,300,373 to Shackle; U.S. Pat. No. 5,399,447 to Chaloner-Gill; U.S.Pat. No. 5,411,820 to Chaloner-Gill; U.S. Pat. No. 5,435,054 to Tonderet al.; U.S. Pat. No. 5,463,179 to Chaloner-Gill et al.; U.S. Pat. No.5,482,795 to Chaloner-Gill.; U.S. Pat. No. 5,660,948 to Barker; U.S.Pat. No. 5,869,208, to Miyasaka; U.S. Pat. No. 5,882,821 to Miyasaka;U.S. Pat. No. 5,616,436 to Sonobe. et al.; and U.S. Pat. No. 6,306,215to Larkin, the teachings of all of which are incorporated herein byreference. Other configurations of cells 26 are possible.

Referring to FIG. 3, an exemplary arrangement of monitoring device 16 isshown according to one embodiment. Monitoring device 16 can includemonitoring circuitry configured to perform monitoring operations, forexample, with respect to battery 14 and/or an environment in whichbattery assembly 13 resides for use in one embodiment. In the depictedconfiguration, monitoring device 16 includes an interface 18, processingcircuitry 30, storage circuitry 32, a voltage sensor 34, a currentsensor 36, and a temperature sensor 38. Other embodiments of monitoringdevice 16 are possible including more, less and/or alternativecomponents. For example, a user interface, such as a visual display, maybe included in some embodiments to convey information regardingelectrical system 10 to a user. In one example, processing circuitry 30may control a user interface to convey state of charge informationregarding battery 14 at different moments in time and at differentstates of charge.

In one embodiment, processing circuitry 30 is arranged to process data,control data access and storage, issue commands, and control otherdesired operations. Processing circuitry 30 may comprise circuitryconfigured to implement desired programming provided by appropriatemedia in at least one embodiment. For example, the processing circuitry30 may be implemented as one or more of a processor and/or otherstructure configured to execute executable instructions including, forexample, software and/or firmware instructions, and/or hardwarecircuitry. Exemplary embodiments of processing circuitry 30 includehardware logic, PGA, FPGA, ASIC, state machines, and/or other structuresalone or in combination with a processor. These examples of processingcircuitry 30 are for illustration and other configurations are possible.

Storage circuitry 32 is configured to store programming such asexecutable code or instructions (e.g., software and/or firmware),electronic data, databases, or other digital information and may includeprocessor-usable media 33. Processor-usable media 33 may be embodied inany computer program product(s) or article of manufacture(s) which cancontain, store, or maintain programming, data and/or digital informationfor use by or in connection with an instruction execution systemincluding processing circuitry in the exemplary embodiment. For example,exemplary processor-usable media 33 may include any one of physicalmedia such as electronic, magnetic, optical, electromagnetic, infraredor semiconductor media. Some more specific examples of processor-usablemedia include, but are not limited to, a portable magnetic computerdiskette, such as a floppy diskette, zip disk, hard drive, random accessmemory, read only memory, flash memory, cache memory, and/or otherconfigurations capable of storing programming, data, or other digitalinformation.

At least some embodiments or aspects described herein may be implementedusing programming stored within appropriate storage circuitry 32described above and/or communicated via a network or other transmissionmedia and configured to control appropriate processing circuitry 30. Forexample, programming may be provided via appropriate media including,for example, embodied within articles of manufacture, embodied within adata signal (e.g., modulated carrier wave, data packets, digitalrepresentations, etc.) communicated via an appropriate transmissionmedium, such as a communication network (e.g., the Internet and/or aprivate network), wired electrical connection, optical connection and/orelectromagnetic energy, for example, via a communications interface, orprovided using other appropriate communication structure or medium.Exemplary programming including processor-usable code may becommunicated as a data signal embodied in a carrier wave in but oneexample.

Voltage sensor 34 is configured to monitor one or more voltage ofbattery 14 in the described implementation. For example, voltage sensor34 may be configured to monitor voltages of individual cells 26 as wellas the entire voltage of battery 14 in one embodiment. It may be desiredto measure the voltage of cell 1 (i.e., the cell coupled with ground) insome embodiments employing a plurality of cells 26 to obtain the mostaccurate voltage measurement of an individual cell of battery 14 iflevel shifting circuitry is employed between the remaining cells andanalog-to-digital (A/D) sampling circuitry (not shown). The voltage ofcell 1 is referred to as V_(cell1) below and the remaining cells 26 ofbattery 14 other than cell 1 may be referred to as upper cells.

Current sensor 26 is configured to measure current into and/or out ofbattery 14 during charging and/or discharging of battery 14 in oneembodiment. Current sensor 26 may be configured to monitor the currentat the negative terminal 22 of battery 14 in one embodiment.

As mentioned above, monitoring device 16 may additionally monitorconditions regarding the environment in which battery 14 resides atdifferent moments in time. In the depicted embodiment, temperaturesensor 38 is configured to provide information regarding the ambienttemperature of the environment about battery assembly 13. Otherenvironmental conditions may be monitored in other embodiments.

Monitoring device 16 may be additionally configured to monitor state ofcharge of battery 14 and may be referred to as state of chargemonitoring circuitry in one arrangement. Monitoring device 16 may conveystate of charge information, for example by a user interface located atload 12 and/or battery assembly 13 in exemplary embodiments, atdifferent moments in time of charging and/or discharging of battery 14.As described in further detail below, processing circuitry 30 may beconfigured to perform a plurality of methods described herein atdifferent moments in time using information of one or more sensors 34,36, 38 and/or discharge voltage profiles of cells 26 to provide state ofcharge information according to one embodiment.

Processing circuitry 30 may utilize a first method, which may bereferred to as Model 1, at appropriate moments in time to provide stateof charge information of battery 14. Model 1 uses Coulomb counting whichmay be modified using temperature profile information of cells 26 in oneembodiment. More specifically, the state of charge (SOC) of Model 1 isdetermined in one configuration as:

$\begin{matrix}{{{Model}\; 1\; S\; O\; C} = \frac{{LearnedCapacity} - {CountedCapacity}}{LearnedCapacity}} & {{Eqn}.\mspace{14mu} 1}\end{matrix}$Counted capacity of Eqn. 1 may be accumulated by integrating batterycurrent as provided by current sensor 36 with respect to time. The Model1 SOC may be calculated by comparing the value of counted capacity to alearned capacity (which may be modified by temperature of theenvironment as discussed further below). Usage of the learned capacityaccommodates for decreasing capacity of the aging of cells 26. Uponinitial manufacture of cells 26, the learned capacity may be set to adefault value, such as corresponding to a nominal capacity of fullycharged cells. Thereafter, learned capacity may be calculated atdifferent moments in time and corresponding to use of the battery 14. Inone embodiment, the learned capacity may be recalculated at moments intime when the state of charge of battery 14 drops below 20%. Arecalculated value may be used in Eqn. 1 until the battery 14 is fullycharged and the state of charge again drops below 20% in one embodiment.

During recalculation, the learned capacity may be adjusted based on thecounted capacity with respect to present temperature and the reportedstate of charge which may be equal to the last state of chargedetermined by processing circuitry 30. In one embodiment, learnedcapacity may be determined by:

$\begin{matrix}{{LearnedCapacity} = \frac{{CountedCapacity}(T)}{{100\%} - {{reported}\; S\; O\; C}}} & {{Eqn}.\mspace{14mu} 2}\end{matrix}$where T may be used to adjust the counted capacity by the temperature ofthe environment. For example, if a cell 26 is at −20° C. and it is known(e.g., from an empirical temperature profile of the cell) that the cell26 will only deliver 50% of its capacity for a typical discharge rate atthe temperature, then the counted capacity may be divided by thepercentage of the capacity (e.g., 50%). Usage of Eqn. 2 provides a ratioof the amount of capacity used versus the amount of capacity believed tobe remaining at a given moment in time. In addition, the learnedcapacity may be determined during one discharge cycle of battery 14 andthe determined learned capacity may be used in Eqn. 1 to determine stateof charge of battery 14 during a different, subsequent discharge cycleof the battery 14.

Referring again to Eqn. 1, the value of learned capacity may be furtheradjusted according to the temperature profile of the type and chemistryof cells 26 being utilized. For example, if the cell 26 is at −20° C.and it is known that it will only deliver 50% of its capacity for atypical discharge rate at the given temperature, then the learnedcapacity value may be multiplied by 50%. In the exemplary configurationusing cells 26 which embody Saphion® technology, the cells 26 are notable to deliver their entire charge when at low temperatures. In thissituation, the Model 1 SOC increases as battery 14 is exposed toincreasing temperatures.

During periods of storage or non-use of battery 14, self-discharge maybe approximated. For example, if monitoring device 16 continues to drawcurrent during periods of non-use, the length of time of non-use may bemonitored and used in conjunction with a determined value indicative ofthe load of monitoring device 16 to estimate self-discharge. Thedetermined self-discharge for a given period of non-use may be used toadjust the counted capacity value of Eqn. 1. The counted capacity may bereset to zero when a full charge is completed (e.g., detected bymonitoring charge current and voltage of cells 26) in one embodiment.

As mentioned above, processing circuitry 30 may utilize a plurality ofmethods to monitor state of charge of battery 14 at different moments intime. Processing circuitry 30 may use one or more discharge voltageprofile to monitor state of charge according to at least one additionalmethod. The profiles may be empirically determined using the specificcells 26 employed within battery 14. The profiles may include SOC slopeand offset values over a plurality of voltage segments (e.g., eight)corresponding to voltages of cells 26. The SOC slope and offset valuesmay be stored for a plurality of discharge current rates (e.g., five)over a plurality of temperatures (e.g., six different temperatureswithin a range of −20 to 70 degrees). Profiles of increased or lesseraccuracy may be used in other embodiments.

According to the presently described method, the initial state of chargeof cells 26 may be calculated using two discharge voltage profilesadjacent to an observed discharge current. The initial state of chargemay be calculated using a weighted average (e.g., linear interpolation)of the two temperature curves adjacent to the observed temperature ofthe environment of use. The Model 2 SOC may thereafter be determined bycombining the discharge voltage profiles using a weighted average (e.g.,linear interpolation) to the observed discharge current.

In one example, if a five Amp-hour battery is being discharged at acurrent of 3.2 Amps, and temperature is 33° C. and five stored dischargevoltage profiles at 0.625, 1, 2.5, 5 and 10 Amps, each containingprofiles for six temperature ranges at −20, −10, 0, 10, 22 and 45° C.,then four results are initially calculated including the SOC at 2.5 Ampsand 22° C., the SOC at 2.5 Amps and 45° C., the SOC at 5 Amps and 22°C., and the SOC at 5 Amps and 45° C. The two SOC calculations at 2.5Amps may be averaged using a weighting between 22° C. and 45° C. for theobserved temperature of 33° C. The process may be repeated for thecalculations at 5 Amps. The two SOC results at 2.5 Amps and 5 Amps maybe averaged using a weighting between 2.5 Amps and 5 Amps for theobserved current of 3.2 Amps in the described example to provide theModel 2 SOC. For a given discharge current and temperature for theabove-described cells 26, the relationship between voltage and state ofcharge is stable over the cycle life of cells 26. In one embodiment, thevoltage used in Model 2 is equal to the voltage of the cell having thelowest voltage.

Accordingly, in the exemplary embodiment employing Models 1 and 2described above, processing circuitry 30 may be configured to monitordifferent electrical parameters of battery 14 to provide the state ofcharge information. For example, as discussed above, processingcircuitry 14 may be configured to monitor discharge current of battery14 (e.g., with respect to Coulomb counting) during Model 1 and tomonitor voltage of at least one cell 26 of battery during Model 2 in thedescribed examples.

The above-described exemplary Models 1 and 2 may be used in a pluralityof methods by processing circuitry 30 to determine the state of chargeof battery 14 at different moments in time. In addition, the Models 1and 2 may be used separately or in combination with one another todetermine state of charge of battery 14 at different moments in time inexemplary embodiments. In the exemplary embodiment described below, fourmethods (referred to as SOC Modes 1-4) are used to determine the stateof charge of battery 14 at moments in time determined by correspondingrules set forth below the following discussion of the modes.

In one or more of the following modes, a slew rate control may beprovided where the reported state of charge (i.e., the state of chargeindication provided by processing circuitry 30 for example to the userinterface indicating the state of charge of battery 14) is not permittedto change two times faster than the fastest discharge to which thebattery 14 is capable. Other methods may be used in other embodiments.

For a first of the modes, the reported state of charge (SOC Mode 1) isequal to the state of charge provided by Model 1.

For a second mode, the reported state of charge (SOC Mode 2) iscalculated based on a weighting of both Models 1 and 2 and reliesminimally on Model 1 leading up to the end of discharge (e.g., thismethod relies more upon Model 2 and less on Model 1 over the lastquarter of discharge). One example equation for determining the state ofcharge in the second mode is:reportedSOC=2*SOC*Model1SOC+(100%−2*SOC)*Model2SOC  Eqn. 3where SOC as used in Eqn. 3 is the last reported state of charge. Thelast reported state of charge value may be stored in storage circuitry32 in one embodiment. The value may be stored upon shut down andrecalled at boot-up and the reported state of charge may be initializedto the stored value in one embodiment. If battery 14 is provided instorage, Model 1 immediately reflects the initialized value, and thereported state of charge may be corrected within a few iterations afterboot-up. The state of charge of Mode 2 may be averaged over a desiredtime period, such as thirty seconds, in one embodiment.

For a third mode, the reported state of charge (SOC Mode 3) may becalculated based on a weighting of Model 1 by the following exemplaryequation:reportedSOC=2*Model1*(100%−SOC)  Eqn. 4where SOC as used in Eqn. 4 is the last reported state of charge. Eqn. 4is derived from replacing Model 2 in Eqn. 3 with two times Model 1.

For a fourth mode, the reported state of charge (SOC Mode 4) is equal tothe state of charge provided by Model 2. The reported state of chargemay correspond to the values provided by Model 2 averaged over desiredtime period, such as thirty seconds, in one embodiment.

In one embodiment, mode control rules may be defined to control themethods used by processing circuitry 30 to monitor and/or provideinformation regarding state of charge of battery 14. Processingcircuitry 30 may be programmed to implement the rules in one embodiment.The described rules are exemplary for the described embodiment and more,less and/or alternative rules may be provided in other embodiments.

Processing circuitry 30 may operate in SOC Mode 1 when battery 14 isfully charged. During operations in SOC Mode 1, the processing circuitry30 switches to SOC Mode 2 if the state of charge falls below a threshold(e.g., 50% or lower). In one implementation, when entering SOC Mode 2from SOC Mode 1, the voltage used in Model 2 is V_(cell1) of cell 1discussed above.

Voltage values of individual ones of the cells 26 may be recorded onstartup of electrical system 10. In SOC Mode 2, if any of the voltagevalues of the upper cells increases more than 40 mV, then SOC Mode 2uses the voltage of the cell having the lowest voltage in Model 2. Thisrule accommodates an out of balance situation in SOC Mode 2.

In SOC Mode 2, if the state of charge of Model 2 is greater than thestate of charge than Model 1 times two, then the processing circuitry 30switches to SOC Mode 3. This rule accommodates an occurrence that aftera partial charge the state of charge of Model 2 is not accurate untilbattery 14 is loaded and also addresses an overly conservative learnedcapacity.

In SOC Mode 3, if Model 2 is less than or equal to Model 1 times twothen processing circuitry 30 switches to SOC Mode 2.

In any of the SOC Modes 1-3, if the state of charge of any cell 26 isdetected at or below 10% without averaging then the algorithm switchesto SOC Mode 4.

In any of the SOC Modes 1-3, if the state of charge of Model 1 isgreater than the state of charge of Model 2, and the difference isgreater than 50% of the reported state of charge, the processingcircuitry 30 may switch to SOC Mode 4. This rule accommodates an overlyoptimistic learned capacity.

With the following exceptions, the processing circuitry 30 remains in aselected SOC Mode through periods of non-use of battery 14. In SOC Mode2, the processing circuitry 30 switches to SOC Mode 1 if battery 14receives charge providing the state of charge of Model 1 above 50%. InSOC Mode 4, the processing circuitry 30 switches to SOC Mode 2 ifbattery 14 receives any charge less than a full charge or battery 14 isnot charged or discharged for a period of time (e.g., 10 seconds).During SOC Mode 2, the processing circuitry 30 may use a voltage of thecell 26 having the lowest voltage in Model 2. Processing circuitry 30moves to SOC Mode 1 following a full charge of battery 14 and completionof a balancing procedure to balance the cells 26.

The state of charge may be latched and stored by storage circuitry 32 ifit reaches 0% in one configuration. The state of charge of battery 14 isreported as 0% until charge current is detected in one embodiment.

In one embodiment, the state of charge of Model 1 does not go lower than10% unless processing circuitry 30 is operating in SOC Mode 2 to preventan overly conservative learned capacity from being corrected.

During typical operations, the reported state of charge is provided bySOC Mode 1 with a balanced battery 14 in normal operation. After SOCMode 1, the processing circuitry 30 may move to SOC Mode 2 when thestate of charge is <=50% and then SOC Mode 4 when the state of charge ofany cell 26 is detected at or below 10%:

Discharging of batteries may involve different patterns in differentapplications. In an exemplary transportation application, differentpatterns may correspond to regularity of use, terrain, style, chargeopportunity and temperature. In one embodiment, monitoring and providinginformation regarding state of charge may utilize information regardingcapacity observed over a user's previous discharge pattern or cycle.Accordingly, the Model 1 SOC discussed above may have increased accuracyif a user operates a load 12 and charger 20 in a similar manner fromfull charge to a knee of the discharge voltage profile (e.g., the pointin the profile where the relatively flat profile starts to change at amore significant rate) as a previous use.

As described above, some aspects of the disclosure provide state ofcharge information of a battery. At least one of the above-describedaspects may be used with batteries having substantially flat dischargevoltage profiles with increased accuracy over pure Coulomb countingstrategies or strategies using learning functions which occurperiodically over a life of the battery after a complete charge followedby a complete discharge. For example, pure Coulomb counting may beperiodically adjusted (e.g., at full charge or complete discharge) tocorrect for inaccuracies. In addition, strategies which use learningfunctions typically can not provide accurate state of charge informationleading up to or during the learning cycle (e.g., the state of chargeindication may be overly conservative leaving usable energy within thebattery when a charge is indicated to be needed, may be overlyoptimistic leaving the customer without warning of a dead battery and/ormay fluctuate with temperature). Also, impedance monitoring solutionsmay not be applicable to cells whose impedance is substantially constantuntil the very end of discharge (e.g., lithium-phosphate cells).

According to one embodiment described above, a learning function basedupon previous usage of the battery is implemented to increase accuracyof state of charge information during subsequent uses. The learningfunction is automatic without user input in at least one configuration.Furthermore, one embodiment of the disclosure accommodates temperatureand reduces affects of temperature upon state of charge indications.Some embodiments provide state of charge information in multiple cellbattery arrangements and in states where the cells may be out of balancewith one another. As further disclosed above according to oneimplementation, a linear state of charge calculation reaching 0% isprovided when the available energy of the battery has been used. Inaddition, accuracies of less than 1% error are believed provided between10% state of charge and fully discharged, and less than 5% error between100% and 10% state of charges in some configurations. Additionally, atleast one embodiment accounts for self-discharge during periods ofnon-use of the battery.

In compliance with the statute, the invention has been described inlanguage more or less specific as to structural and methodical features.It is to be understood, however, that the invention is not limited tothe specific features shown and described, since the means hereindisclosed comprise preferred forms of putting the invention into effect.The invention is, therefore, claimed in any of its forms ormodifications within the proper scope of the appended claimsappropriately interpreted in accordance with the doctrine ofequivalents.

Further, aspects herein have been presented for guidance in constructionand/or operation of illustrative embodiments of the disclosure.Applicant(s) hereof consider these described illustrative embodiments toalso include, disclose and describe further inventive aspects inaddition to those explicitly disclosed. For example, the additionalinventive aspects may include less, more and/or alternative featuresthan those described in the illustrative embodiments. In more specificexamples, Applicants consider the disclosure to include, disclose anddescribe methods which include less, more and/or alternative steps thanthose methods explicitly disclosed as well as apparatus which includesless, more and/or alternative structure than the explicitly disclosedstructure.

1. A method for determining a reported state of charge of a batterysystem, the method comprising: determining the reported state of chargeaccording to a first method when a previous state of charge is greaterthan a first threshold percentage and less than or equal to 100%;determining the reported state of charge according to a second methodwhen the previous state of charge is greater than a second thresholdpercentage and less than or equal to the first threshold percentage;determining the reported state of charge according to a third methodwhen the previous state of charge is greater than or equal to 0% andless than or equal to the second threshold percentage.
 2. The method ofclaim 1 wherein: determining the reported state of charge according tothe first method comprises monitoring a monitored current of the batterysystem; and determining the reported state of charge according to thethird method comprises monitoring a voltage of a cell of the batterysystem.
 3. The method of claim 2 wherein determining the reported stateof charge according to the second method comprises combining informationof the first and third methods.
 4. The method of claim 3 whereindetermining the reported state of charge according to the first methodfurther comprises counting coulombs of the monitored current of thebattery system.
 5. The method of claim 3 wherein determining thereported state of charge according to the first method further comprisesdetermining an estimated state of charge based on an estimated capacityof the battery system and the counted coulombs of the monitored currentof the battery system.
 6. The method of claim 3 wherein determining thereported state of charge according to the third method further comprisesdetermining an estimated state of charge using at least onepredetermined discharge voltage model.
 7. The method of claim 6,wherein: the at least one predetermined discharge voltage model isselected from a plurality of possible discharge voltage model accordingto a current and a temperature of the cell; and the estimated state ofcharge is determined to be the state of charge of the at least onedischarge voltage model according to a measured voltage of the cell. 8.The method of claim 1, further comprising calculating a learned capacityof the battery system using the reported state of charge of the batterysystem and a coulomb discharge value.
 9. The method of claim 1, furthercomprising determining the reported state of charge according to thefirst method when a charge current is present in the battery system. 10.An apparatus for determining a reported state of charge of a batterysystem, the apparatus comprising a computer processor and a computermemory operatively coupled to the computer processor, the computermemory having disposed within it computer instructions capable of:determining the reported state of charge according to a first methodwhen a previous state of charge is greater than a first thresholdpercentage and less than or equal to 100%; determining the reportedstate of charge according to a second method when the previous state ofcharge is greater than a second threshold percentage and less than orequal to the first threshold percentage; determining the reported stateof charge according to a third method when the previous state of chargeis greater than or equal to 0% and less than or equal to the secondthreshold percentage.
 11. The apparatus of claim 10 wherein: determiningthe reported state of charge according to the first method comprisesmonitoring a monitored current of the battery system; and determiningthe reported state of charge according to the third method comprisesmonitoring a voltage of a cell of the battery system.
 12. The apparatusof claim 11 wherein determining the reported state of charge accordingto the second method comprises combining information of the first andthird methods.
 13. The apparatus of claim 12 wherein determining thereported state of charge according to the first method further comprisescounting coulombs of the monitored current of the battery system. 14.The apparatus of claim 12 wherein determining the reported state ofcharge according to the first method further comprises determining anestimated state of charge based on an estimated capacity of the batterysystem and the counted coulombs of the monitored current of the batterysystem.
 15. The apparatus of claim 12 wherein determining the reportedstate of charge according to the third method further comprisesdetermining an estimated state of charge using at least onepredetermined discharge voltage model.
 16. The apparatus of claim 15,wherein: the at least one predetermined discharge voltage model isselected from a plurality of possible discharge voltage model accordingto a current and a temperature of the cell; and the estimated state ofcharge is determined to be the state of charge of the at least onedischarge voltage model according to a measured voltage of the cell. 17.The apparatus of claim 10 wherein the computer memory further includescomputer instructions capable of calculating a learned capacity of thebattery system using the reported state of charge of the battery systemand a coulomb discharge value.
 18. The apparatus of claim 10 wherein thecomputer memory further includes computer instructions capable ofdetermining the reported state of charge according to the first methodwhen a charge current is present in the battery system.
 19. A computerprogram product embodied on a tangible computer-readable medium fordetermining a reported state of charge of a battery system, the computerprogram product comprising: computer program instructions fordetermining the reported state of charge according to a first methodwhen a previous state of charge is greater than a first thresholdpercentage and less than or equal to 100%; computer program instructionsfor determining the reported state of charge according to a secondmethod when the previous state of charge is greater than a secondthreshold percentage and less than or equal to the first thresholdpercentage; computer program instructions for determining the reportedstate of charge according to a third method when the previous state ofcharge is greater than or equal to 0% and less than or equal to thesecond threshold percentage.
 20. The computer program product of claim19 wherein: determining the reported state of charge according to thefirst method comprises monitoring a monitored current of the batterysystem; and determining the reported state of charge according to thethird method comprises monitoring a voltage of a cell of the batterysystem.
 21. The computer program product of claim 20 wherein determiningthe reported state of charge according to the second method comprisescombining information of the first and third methods.
 22. The computerprogram product of claim 21 wherein determining the reported state ofcharge according to the first method further comprises counting coulombsof the monitored current of the battery system.
 23. The computer programproduct of claim 21 wherein determining the reported state of chargeaccording to the first method further comprises determining an estimatedstate of charge based on an estimated capacity of the battery system andthe counted coulombs of the monitored current of the battery system. 24.The computer program product of claim 21 wherein determining thereported state of charge according to the third method further comprisesdetermining an estimated state of charge using at least onepredetermined discharge voltage model.
 25. The computer program productof claim 24, wherein: the at least one predetermined discharge voltagemodel is selected from a plurality of possible discharge voltage modelaccording to a current and a temperature of the cell; and the estimatedstate of charge is determined to be the state of charge of the at leastone discharge voltage model according to a measured voltage of the cell.26. The computer program product of claim 19, further comprisingcomputer program instructions for calculating a learned capacity of thebattery system using the reported state of charge of the battery systemand a coulomb discharge value.
 27. The computer program product of claim19, further comprising computer program instructions for determining thereported state of charge according to the first method when a chargecurrent is present in the battery system.